Fluid Mixing System For Pumping Devices And Methods For Use With Medical Fluids

ABSTRACT

A fluid mixing system including an extending channel, at least two fluid inlet ports in fluid connection with the extending channel, at least one outlet port in fluid connection with the extending position between the two fluid inlet ports and a sealing member in sealing engagement with the extending channel is described. The sealing member may be movable within the extending channel to adjust the volumetric ratio of the two fluids delivered through the outlet port.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of and claims priority toU.S. application Ser. No. 13/071,939, filed Mar. 25, 2011 and entitled“Pumping Devices, Systems Including Multiple Pistons and Methods for Usewith Medical Fluids.” This application may contain subject matter thatis related to that disclosed in application Ser. No. 12/974,549, filedon Dec. 21, 2010, the contents of which are incorporated herein byreference.

BACKGROUND

The following information is provided to assist the reader to understandthe devices, systems and/or methods described herein and the environmentin which such devices, systems and/or methods will typically be used.The terms used herein are not intended to be limited to any particularnarrow interpretation unless clearly stated otherwise in this document.References set forth herein may facilitate understanding of the devices,systems and/or methods or the background. The disclosure of allreferences cited herein are incorporated by reference.

In many medical procedures, such as drug delivery, it is desirable toinject a fluid into a patient. Likewise, numerous types of contrastmedia (often referred to simply as contrast) are injected into a patientfor many diagnostic and therapeutic imaging procedures. For example,contrast media are used in diagnostic procedures such as X-rayprocedures (including, for example, angiography, venography andurography), CT scanning, magnetic resonance imaging (MRI), andultrasonic imaging. Contrast media are also used during therapeuticprocedures, including, for example, angioplasty and other interventionalradiological procedures. Regardless of the type of procedure, any fluidinjected into the patient must be sterile and contain a minimum ofpyrogens.

In the case of relatively high pressure applications, such as CT andangiography, mechanized syringe injectors are often used. In general,syringe pumps can deliver a fluid with good control of both pressure andflow rate. However, flow rate acceleration of syringe injectors islimited by the inertia of the extensive drive train required totranslate motor rotation into syringe plunger motion. Moreover, syringepumps are limited in that the maximum volume that can be injected at onetime is the volume of the syringe.

Various pump systems for generally continuous delivery of fluids fromlarge volume sources of fluid are available. However, it is oftendifficult to accurately control the pressure and flow rate of the fluidexiting the pumping system. In relatively low pressure applications, forexample, peristaltic pumps have long been used. However, peristalticpumps are difficult to control with accuracy.

Cost-effective and efficient pumping systems including a plurality ofpressurizing members actuated in a timed manner to providepressurization for injection of contrast and other liquid media are, forexample, described in U.S. Pat. Nos. 6,197,000 and 5,916,197. Althoughsuch pumps provide good control of pressure and flow rate, some variancein the pressure and/or flow rate can be experienced. Timed or sequentialactuation of a plurality of pressurizing member or elements (forexample, pistons, vanes, etc.) can, for example, result in pulsatilevariations in pressure and/or flow rate. In general, pulsatilevariations are repetitive variations or variations that occur with acertain frequency (for example, the frequency of activation of thepressurizing member(s)). U.S. patent application Ser. No. 12/974,549discloses a number of compensating systems to reduce pulsatile flow inpump systems including a plurality of pressurizing members actuated in atimed manner.

SUMMARY

In a number of embodiments hereof, a fluid delivery system includes apump system including a plurality of pressurizing members in whichpulsatility arising from timed actuation of the pressurizing members isreduced or minimized. Such pump systems provide control of fluidpressure and flow rate over a broad range of operating pressures (forexample, over operating pressures used in the injection of variouscontrast media and/or other medical fluids into a patient). The pumpsystems hereof can, for example, be used in connection with acompensating system or systems as disclosed in U.S. patent applicationSer. No. 12/974,549 or can be used without such a compensating system orsystems. In a number of embodiments, profiles of cam lobes of a camshaft used to drive, for example, a plurality of pistons are adapted toreduce or eliminate pulsatility. In a number of other embodiments,independent control of each of a plurality of pressurizing members suchas pistons is effected to reduce or eliminate pulsatility. In the caseof independent control, feedback of data can be provided to one or moreprocessors from one or more sensors to effect control in the manner of aservomechanism. The system can, for example, anticipate required needsand use servo feedback to fine tune or adjust the system variables orparameters to achieve a desired result of flow with little or nopulsatility.

In one aspect, a system for delivery of a medical fluid to a patientincludes a pump system including a plurality of at least three chambers.Each of the plurality of chambers includes an inlet through which fluidis drawn into the chamber and an outlet from which fluid is expelledfrom the chamber. The pump system further includes a common outletchannel in fluid communication with the outlet of each of the pluralityof chambers and a plurality of at least three pistons. Each of thepistons is slidably disposed within a respective one of the plurality ofchambers. The system further includes a drive system including a camshaft including a plurality of at least three cam lobes. Each of theplurality of cam lobes has a profile. The drive system further includesa plurality of at least three cam lobe followers. Each of the cam lobefollowers is in operative connection with a respective one of theplurality of cam lobes and is adapted to be placed in operativeconnection with a respective one of the plurality of pistons.

The profile of each of the plurality of cam lobes is adapted to providea transient increase or spike in calculated theoretical output of thepump system to reduce periodic variation in measured output thereof. Thetransient increase or spike in calculated theoretical output of the pumpsystem can, for example, include an increase from a generally constanttheoretical output, a maximum and a subsequent decrease to the generallyconstant theoretical output. The profile of each of the cam lobes can,for example, include a fluid delivery phase including an accelerationportion, a constant velocity portion and a deceleration portion.

In a number of embodiments, each of the plurality of pistons is inremovable connection with a one of a plurality of cam lifters at a firstend of the cam lifter, and one of the plurality of cam lobe followers isconnected to the second end of each of the plurality of cam lifters.

In a number of embodiments, the plurality of at least three chambersincludes five chambers, the plurality of at least three pistons includesfive pistons, the plurality of at least three cam lobes includes fivecam lobes, and the plurality of at least three cam lobe followersincludes five cam lobe followers.

The system can further include a plurality of five cam lifters eachhaving a first end and a second end. The first end of each of the camlifters can be in removable connection with a respective one of the fivepistons and the second end of each of the cam lifters is connected to arespective one of the five cam lobe followers. Each of the cam lifterscan be in operative connection with a biasing element to retain theconnected cam lobe follower in contact with the associated cam lobeduring a chamber filling phase of the cam lobe profile. The biasingelement can, for example, include a spring positioned within the camlifter.

The system can further include five extending members, each of whichpasses through an extending passage defined in each of the five camlifters to limit rotation of each of the cam lifters about alongitudinal axis thereof. Each of the cam lifters is movable relativeto the extending member in the direction of the longitudinal axis of thecam lifter. Each of the biasing element/springs can abut the respectiveextending member at a first end thereof and an abutment member connectedto the respective cam lifter at a second end thereof.

The pump system can further include a fluid intake system in fluidconnection with the inlets of the plurality of chambers. In a number ofembodiments, the fluid intake system includes at least two fluid inletports and a control system to adjust the volumetric ratio of fluiddelivered from the fluid inlet ports. The fluid intake system canfurther include an extending channel in fluid connection with each ofthe fluid inlet ports. The fluid inlet ports can, for example, be spacedalong the extending channel. The control member can, for example,include a sealing member in sealing engagement with the channel. Thesealing member is movable within the channel to adjust the volumetricratio. The fluid intake system can further include a plurality of spacedoutlet ports in fluid connection with the extending channel and with theinlets of the plurality of chambers. The spaced outlet ports can, forexample, be positioned within the channel between the positions of thefluid inlets.

In another aspect, a system for delivery of a medical fluid to a patientincludes a pump system including a plurality of at least three chambers.Each of the plurality of chambers includes a piston slidably disposedtherein. Each of the chambers includes an inlet through which fluid isdrawn into the chamber and an outlet from which fluid is expelled fromthe chamber. The outlet of each of the plurality of chambers is in fluidconnection with a common outlet channel. The system further includes acam shaft including a plurality of at least three cam lobes. Each of theplurality of pistons is in operative connection with one of theplurality of cam lobes via one of a plurality of at least three cam lobefollowers. The system also includes a fluid intake system in fluidconnection with the inlets of the plurality of chambers. The fluidintake system includes at least two fluid inlet ports and a controlsystem to adjust the volumetric ratio of fluid delivered from the fluidinlet ports.

As described above, the fluid inlet system can include an extendingchannel in fluid connection with each of the fluid inlets of the fluidinlet system. The fluid inlets can be spaced along the extendingchannel. The control member can, for example, include a sealing memberin sealing engagement with the channel, wherein the sealing member ismovable within the channel to adjust the volumetric ratio of the twofluids. The fluid inlet system can further include a plurality of spacedports in fluid connection with the extending channel. The spaced portsare in fluid connection with the inlets of the plurality of chambers.The spaced ports can, for example, be positioned within the channelbetween the positions of the fluid inlets.

In a further aspect, a system for delivery of a medical fluid to apatient includes a pump system including a plurality of at least twochambers. Each of the plurality of chambers includes a piston slidablydisposed therein. Each of the chambers includes an inlet through whichfluid is drawn into the chamber and an outlet from which fluid isexpelled from the chamber. The outlet of each of the plurality ofchambers is in fluid connection with a common outlet channel. Each ofthe plurality of pistons is in operative connection with a one of aplurality of drive systems that is controlled independently of theothers of the plurality of drive systems. In a number of embodiments,the pump system comprises at least three chambers and at least threepistons. The pump system can, for example, include at least fivechambers and at least five pistons. At least one of the drive systemscan, for example, included a rotary motor operatively connected to oneof the plurality of pistons via a linear drive. At least one of theplurality of drive systems can, for example, include a linear motor.

In still a further aspect, a fluid mixing system includes an extendingchannel and at least two fluid inlet ports in fluid connection with theextending channel. The at least two fluid inlets ports are positioned atdifferent positions along the extending channel. The fluid mixing systemfurther includes at least one outlet port in fluid connection with theextending channel positioned between the two fluid inlet ports and asealing member in sealing engagement with the channel, the sealingmember being movable within the channel to adjust the volumetric ratioof the two fluids. The fluid mixing system can, for example, furtherinclude a plurality of spaced outlet ports in fluid connection with theextending channel. The spaced ports can be positioned within the channelbetween the positions of the fluid inlets.

The devices, systems and/or methods described herein, along with theattributes and attendant advantages thereof, will best be appreciatedand understood in view of the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates cam lifter and/or piston velocity resulting fromdrive of a cam lifter/piston assembly via rotation of a cam lobe havinga certain cam lobe profile.

FIG. 1B illustrates a cam lifter/piston velocity, which is equivalent totheoretical flow velocity depending on the cam rotation speed, for apump including three cam lobes having the cam lobe profile of FIG. 1A.

FIG. 1C illustrates the output (pressure as a function of degree ofrotation) of a three-cam pump having the cam lobe profile of FIGS. 1A-1Band demonstrating substantial variation in pressure or pulsatility.

FIG. 1D illustrates piston velocity as a function of degree of rotationfor a cam lobe designed to exhibit faster acceleration and make theconstant velocity portion of the cam longer than the embodiment of FIG.1A.

FIG. 1E illustrates a theoretical flow profile of a pump including threecam lobes as described in FIG. 1D.

FIG. 1F illustrates the measured pressure output from the three-cam pumpof FIG. 1E, showing the effect of the change to the cam lobe profile.

FIG. 1G illustrates the measured pressure output from the three-cam pumpof FIG. 1E including both a compensating system as illustrated in FIG.2A of U.S. patent application Ser. No. 12/974,549 and a compensatingsystem as described in FIG. 4A of U.S. patent application Ser. No.12/974,549, the disclosure of which is incorporated herein by reference.

FIG. 2A illustrates a perspective, exploded view of an embodiment of apump system.

FIG. 2B illustrates another perspective, exploded view of an embodimentof a pump system.

FIG. 2C illustrates a perspective view of the pump system of FIG. 2A.

FIG. 2D illustrates another perspective view of the pump system of FIG.2A.

FIG. 2E illustrates cam lifter and/or piston velocity resulting fromdrive of a cam lifter/piston assembly via rotation of a cam lobe havinga certain cam lobe profile.

FIG. 2F illustrates a cam lifter/piston velocity for each chamber,theoretical total output, and theoretical fill rate for a pump includingfive cam lobes having the cam lobe profile of FIG. 2E.

FIG. 2G illustrates the measured pressure output from the five-cam pumpof FIG. 2F.

FIG. 2H illustrates cam lifter and/or piston velocity resulting fromdrive of a cam lifter/piston assembly via rotation of a cam lobe havinga different cam lobe profile from that of FIG. 2E.

FIG. 2I illustrates a cam lifter/piston velocity for each chamber,theoretical total output, and theoretical fill rate for a pump includingfive cam lobes having the cam lobe profile of FIG. 2H.

FIG. 2J illustrates the measured pressure output from the five-cam pumpof FIG. 2I.

FIG. 3A illustrates a cross-sectional view of the pump system of FIG.2A.

FIG. 3B illustrates another cross-sectional view of the pump system ofFIG. 2A.

FIG. 3C illustrates a cross-sectional view of a piston and cam-followerassembly of the pump system of FIG. 2A, removed from connection with theremainder of the pump system.

FIG. 3D illustrates a perspective view of the piston and cam-followerassembly of FIG. 3C.

FIG. 3E illustrates an exploded, perspective view of the piston andcam-follower assembly of FIG. 3C.

FIG. 4A illustrates a perspective view of the cam shaft of the pumpsystem of FIG. 1A.

FIG. 4B illustrates another perspective view of the cam shaft of thepump system of FIG. 1A.

FIG. 4C illustrates perspective views of each of the cam elements of thecam shaft of FIG. 4A, after removal of the cam elements from connectionwith the shaft.

FIG. 5A illustrates an enlarged, perspective view of a portion of thepump system of FIG. 2A, illustrating an embodiment of a fluid intakesystem to vary the volumetric ratio of two fluids delivered to the pump.

FIG. 5B illustrates a side, partially cutaway view of a portion of thepump system of FIG. 2A.

FIG. 6A illustrates a cross-sectional view of another embodiment of apump system in which the drive of each piston is independentlycontrollable.

FIG. 6B illustrates a cross-sectional view of another embodiment of apump system in which the drive of each piston is independentlycontrollable.

DETAILED DESCRIPTION

As used herein and in the appended claims, the singular forms “a,” “an”,and “the” include plural references unless the content clearly dictatesotherwise. Thus, for example, reference to “a check valve” includes aplurality of such check valves and equivalents thereof known to thoseskilled in the art, and so forth, and reference to “the check valve” isa reference to one or more such check valves and equivalents thereofknown to those skilled in the art, and so forth.

The devices, systems and methods described herein can, for example, beused to pressurize medical fluids for injection into a patient over apressure range of approximately 10 to 2000 psi (and more typically 25 to1500 psi) and over a flow rate range of approximately 0 to 100 ml/sec(and more typically 0 to 50 ml/sec).

U.S. patent application Ser. No. 12/974,549 discloses a number ofmulti-cylinder, pumping devices, systems and methods for use withmedical fluids. These include, for example, pumps having three chambersand pressurizing pistons disposed therein, which are in operativeconnection with a cam shaft to drive motion of the pressurizing pistonswithin the chambers. Various compensating systems are also disclosed toreduce pulsatility in flow.

Pulsatility can, for example, be measured in terms of variations in flowrate or variations in pressure. As set forth in U.S. Pat. Nos. 6,197,000and 5,916,197, a degree or percent of pulsatile flow can be defined withthe following equation:

100%*(max flow−min flow)/average flow

The standard deviation from an average pressure and/or flow rate canprovide another or alternative measure of pulsatility. In general,pressure is more easily measured than flow rate.

In general, flow rate in the system is directly related to pressurechange. In a simple system of flow of an incompressible fluid in a pipe,this direct relationship can be shown from the following equation,derived from the Bernoulli equation:

$p_{B} = {p_{A} - {\rho \; {g\left( {{\Delta \; e} + {f\frac{L}{D}\frac{V^{2}}{2g}}} \right)}}}$

wherein, p_(B) is pressure at point B, p_(A) is pressure at point A, ρis fluid viscosity, g is the gravity acceleration constant, z is pipeelevation above some datum, f is a friction factor, D is pipe diameter,L is pipe length between point A and point B and V is the averagevelocity of the fluid. Likewise, for viscous, incompressible flow in along pipe (that is, having a length significantly longer than itsdiameter) of circular cross-section, the Hagen-Pouiseulle equationprovides

$Q = {{\int_{0}^{R}{2\pi \; v_{z}{r}}} = {\frac{\pi \; R^{4}}{8\mu}\frac{\Delta \; p}{L}}}$

wherein Q is volumetric flow rate, R is the radius of the pipe, μ isdynamic fluid viscosity, L is the length of the pipe and Δp is thepressure change. Although there is no corresponding simple equation toprovide flow rate as a function of pressure in a pump system, the aboveequations are indicative of the direct relationship between flow rateand pressure (for example, as measured in outlet conduit 60 of an outlet64) in a pump system.

A number of multi-chamber or multi-cylinder pump systems were designedto deliver continuous flow with minimal pulsatility. For example, camshafts and associated cam lobes were designed to provide theoreticallyconstant pressures/flows, and other components were selected to providethe best output. However pulsatility remained in the flow. As describedabove, the fluid output associated with a number of cams shaft lobesshould theoretically have been constant for a constant rotationalvelocity of the cam shaft. As the pressure rises, however, and withoutlimitation to any mechanism, it is believed that mechanical capacitance(for example, compression and stretch of components under load) causesdelays in the rise of pressure associated with individual pistons. Asthe delay increases, the system fluid pressure drops in the region ofoverlap of output of the cylinders.

In a number of embodiments of pump systems hereof, the cam lobe profilewas altered to reduce or minimize pulsatility. The cam lobe profiles inseveral representative embodiments of pump systems were basedapproximately upon that of an isosceles trapezoid (referring to thecorresponding velocity profile for a cam lifter and/or piston inoperative connection with the cam lobe) for fluid delivery and fillingof the chambers. As used herein, the term “profile” of a cam lobe refersto the manner in which a radius, as measured from the center of a camshaft about which the cam lobe rotates (see r_(c) in FIG. 4C), variesaround the circumference of the cam lobe. As the variance of radiusr_(c) determines the direction and velocity of a cam lifter and/orpiston in operative connection with the cam lobe upon rotation of thecam lobe, the resultant velocity of the cam lifter and/or piston can beused to describe the cam profile. FIG. 1A, for example, illustrates thevelocity of the cam lifter and/or piston upon rotation of a cam lobe.The velocity is proportional to the flow out of (during a fluid deliveryphase) and into (during a fluid fill phase) one chamber of a pump systemresulting from drive of a piston within the cylinder or chamber of thepump system via rotation of the cam lobe. The base line (line A-D-G)represents where there is no flow into or out of the cylinder of pump.Over the region A-D (the fluid delivery phase), the piston is advancingwithin the chamber, and fluid is being delivered. Over the region D-G(the fluid fill phase), the piston is being retracted within thecylinder and fluid is filling the chamber.

The area A-B-C-D is equal to the piston travel since it is the productof rotational distance and velocity. Also, the area D-E-F-G must havethe same area as the fill area. The distance A-C is equal to 360 degreesdivided by the number of cylinders. For example, for a three-cylinderpump, the distance A-C is 120 degree. For a five-cylinder pump, thedistance A-C is 72 degrees. For an isosceles trapezoid distance, A-B′ isequal to distance C′-D. Therefore, the average velocity is equal to thetotal stroke divided by A-C′ or 120 degrees in the case of athree-cylinder pump. The acceleration (the area A-B-B′) is the averagevelocity divided by the number of degrees that acceleration is desired(distance A-B′). The filling of the pump cylinder is determined in thesame manner. However, the distance A-G cannot exceed 360 degrees.

One embodiment of a cam having a symmetric profile had the followingspecifications.

TABLE 1 Total lift 0.363 Constant acceleration angle 60 Constantvelocity angle 60 Constant deceleration angle 60 Constant velocity0.003025 Constant acceleration 5.04167E−05 Velocity at end of acc0.003025 Position at end of acceleration 0.09075 Position at end ofconst vel. 0.27225 Position at 180 0.363

FIG. 1B illustrates the resultant cam lift profile. The information isequivalent to theoretical flow velocity depending on the cam rotationspeed. FIG. 1C illustrates the output pressure as a function of degreeof rotation for the pump at an average operating pressure ofapproximately 640 pounds per square inch (or psi). As illustrated inFIG. 1C, there was a significant drop in pressure at the point where onecam is accelerating and another cam is decelerating. A variation ofalmost a ±23% in pressure is exhibited.

To address such pressure variation or pulsatility, the cam lobes of thecam shaft were redesigned to make the constant velocity portion of thecam longer and the acceleration portions shorter. In one embodiment, andas illustrated in FIG. 1D, each cam lobe had a start (in the pistonadvance/fluid delivery portion) with an initial acceleration of 0.00029inches/deg² for 7 degrees, then acceleration of 0.00014 inches/deg².This acceleration was followed by 103 degrees of constant velocity of0.300 inches/degree. The deceleration was the reverse acceleration to137 degrees. After 137 degrees the piston was retracting, (and thecylinder is filling). From 350 degrees to 360 degrees, the piston was inthe fully down or retracted position, allowing for extra time forcomplete filling of the piston chamber. FIG. 1E illustrates thetheoretical flow profile of the pump system with three cams as describedabove. The three peaks or periods of increased velocity/flow illustratedin FIG. 1E occur where the pressure drops occurred in the pump of FIG.1C.

FIG. 1F illustrates the pressure output from the three-cam pump system,showing the effect of the change to the cam profile. In that regard, asignificant improvement in the pulsatility was achieved, with a pressurevariation of approximately +7.5% and −25% or approximately ±16%. FIG. 1Gillustrates the pressure output from such a three-cam pump system, butfurther including both a compensating system as illustrated in FIG. 2Aof U.S. patent application Ser. No. 12/974,549 and a compensating systemas described in FIG. 4A of U.S. patent application Ser. No. 12/974,549.The average pressure was 640 psi. and the pressure variation wasapproximately +5% and −8%.

FIGS. 2A through 3B illustrate another representative embodiment of amulti-cylinder pump system 10 including five cylinders or chambers. Inthe illustrated embodiment, five chambers or cylinders 20 (see, forexample, FIG. 3A) of a pressurizing unit 15 are in generally linear,side-by-side alignment (that is, the axes of chambers 20 are generallyin the same plane).

Each chamber 20 has an inlet port 25 and an outlet port 30 in fluidconnection therewith (see, for example, FIG. 3B). Inlet ports 25 andoutlet ports 30 can, for example, be provided with check valves or plugvalves 40 to assist in maintaining the desired direction of flow. Inletports 25 are preferably in fluid connection with an inlet passage,conduit or channel 50, while outlet ports 30 are in fluid connectionwith a common outlet passage, conduit or channel 60.

In the illustrated embodiment (see, for example, FIGS. 2A and 3B), andas further described below, each inlet channel 50 is in fluid connectionwith either or both of an inlet port 54 a or an inlet port 54 b (each ofwhich, can for example, include a barbed connector) for attachment to asource A of a first fluid (such as a contrast medium or otherpharmaceutical/medical fluid) or a source B of a second fluid (forexample, a diluent such as a saline solution). Outlet channel 60 (see,for example, FIG. 3B) can, for example, be in fluid connection with anoutlet port 64 (see, for example, FIG. 2B), which can, for example, bein fluid connection with a connector such as a Luer connector 66.Connector 66 can, for example, connect to a delivery set includingtubing and a catheter to deliver fluid to a patient.

Disposed within each chamber 20 is a pressurizing member or piston 70suitable to alternatively draw the liquid medium into chamber 20 upon adownward or rearward stroke thereof and to expel/pressurize the liquidmedium, forcing the pressurized liquid medium into outlet channel 60,upon an upward or forward stroke thereof. Motive force is provided topistons 70 by, for example, an external motor-driven (or otherwisepowered) drive mechanism or drive system 100 (illustrated schematicallyin FIG. 2A) that imparts reciprocating linear motion to pistons 70. Highpressures (for example, used in contrast medium injection in CT andangiographic procedures) in outlet channel 60 are possible with theproper choice of materials and wall thickness. One or more sealingmembers such as O-rings can be positioned between each piston 70 and theinner wall of chamber 20′ (for example, within seating formed in pistons70) to form a sealing engagement therewith.

In a number of representative embodiments of pump system 10 used in thestudies hereof, the bore diameter of each chamber 20 was approximately0.5 inches and the stroke length of pistons 70 was approximately 0.342inches, resulting in a displacement of 5.5 ml per revolution of camshaft 110 for pump system 10. The chambers and pistons of the pumpsystems hereof can, for example, be dimensioned and operated to providea range of fluid displacements per revolution. In a number ofembodiments, pump systems hereof exhibit a displacement per revolutionin the range of approximately 1 to 10 ml.

As discussed above, drive mechanism 100 (illustrated schematically inbroken lines in FIG. 2A) can, for example, be in inoperative connectionwith a timing mechanism, system or shaft such as a cam shaft 110 todrive pistons 70 in a timed sequence, which can be designed to reduce orminimize pulsatile flow. Drive mechanism 100 (for example, including anelectric motor) is in operative connection with cam shaft 110. Camelements or lobes 112 of cam shaft 110 can, for example, be in operativeconnection with cam lifter assemblies or piston extension members 120which are reciprocally moveable through seatings formed in a lifterblock 122 and terminate on one end thereof in attachment members whichcooperate with corresponding attachment members on pistons 70. Forexample, retention slots 123 on piston extension members 120 cancooperate with flanges 73 (see, for example, FIG. 3A) on pistons 70 toform a readily releasable connection between pistons 70 and pistonextension members 120.

FIG. 2E illustrates piston/lifter velocity versus degree of rotation forone embodiment of cam lobes 112 of pump system 10. During the fluiddelivery phase, the embodiment of FIG. 2E exhibited an area ofacceleration of 0.000132 inches/degree² for 18 degrees, then a constantvelocity of 0.002359 inches/degree for 126 degrees, and then adeceleration of 0.000132 inches/degree² for 18 degrees. During the fluidfill phase, the embodiment of FIG. 2E exhibited an acceleration of0.0000444 inches/degree² (down) for 59 degrees. then a constant velocityof 0.00263 inches/degree for 71 degrees (down), and then a decelerationof 0.0000444 inches/degree² for 58 degrees to the bottom of the stroke.A stationery position followed for 10 degrees to guarantee filling.

Unlike a three-cylinder pump system, in the case of a five-chamber orfive-cylinder pump system, such as pump system 10, there are always atleast two cylinders that provide output or input at any time as seen,for example, in FIG. 2F which illustrates the output for each chamberand the total output of a five-chamber pump. Thus, the flow from acylinder or chamber is at most half of the total output of the pumpsystem at any point in time. When one piston 70 of a chamber 20 isaccelerating, and another piston 70 of another chamber 20 isdecelerating, a third piston 70 of a third chamber 20 is at full outputand is delivering half of the desired flow. The crossover point is wherea pressure drop typically occurs. In the case of a five-chamber pumpsystem, the pressure drop should be half as much as in the three-chamberpump system.

As illustrated in FIG. 2G, which sets forth the outlet pressure of pumpsystem 10 as a function of the degree of pump rotation, pump system 10,with the cam lobe design of FIG. 2E, showed an improvement over thethree-chamber pumps discussed above. FIG. 2G illustrates an averagepressure of 693 psi with a pressure variation of +5.4% and −14%.However, there was more variation than the three-chamber pump whichincluded a compensating system as illustrated in FIG. 2A of U.S. patentapplication Ser. No. 12/974,549 and a compensating system as describedin FIG. 4A of U.S. patent application Ser. No. 12/974,549.

Another embodiment of a cam lobe profile for five-chamber pump system 10is illustrated in FIG. 2H, which sets forth the velocity of the camlifter/piston as a function of the degree of rotation. This cam lobe hada similar profile to that described in connection with FIG. 2E, butexhibited an increase in acceleration and deceleration as compared tothe embodiment of FIG. 2E so that the impact of the crossover wasdecreased. In the fluid delivery/forward piston movement phase, the camlobe profile of FIG. 2H exhibited an acceleration of 0.000295inches/degree² for 10 degrees, then a constant velocity of 0.002295inches/degree for 139 degrees, and then a constant deceleration of0.000295 inches/degree² for 10 degrees. In the chamber fill/reversepiston movement phase, the cam lobe profile of FIG. 2H exhibited aconstant deceleration of 0.000042 inchs/degree² for 65 degrees, then aconstant velocity of 0.0027 inches/degree for 61 degrees, and then anacceleration to the bottom of the stroke of 0.00004175 inches/degree²for 65 degrees. A 10-degree dwell at the bottom of the stroke followedto provide additional fill time.

For a mathematically or theoretically uniform flow with this type of camlobe profile, the constant velocity section would extend to 144 degrees,rather than to 149 degrees as described above. Extending the constantvelocity section or portion by five extra degrees reduces or minimizesthe pressure drop as compared to that exhibited by the cam lobe designof FIG. 2E. Because of the 5 degrees of overlap, there are peaks in thetheoretical total output as illustrated in FIG. 2I. The peaks aredesigned to counteract the periodic pressure drops illustrated in FIG.2G. As illustrated in FIG. 2I, operation of pump system 10 with such camlobe profiles at an average pressure to be 631 psi resulted in apressure variation of approximately +2.8% and −8.5%. Thus, five-chamberpump system 10 provides similar performance to the three-chamber pumpsystem of U.S. patent application Ser. No. 12/974,549 which includesboth compensating systems as illustrated in FIG. 2A and FIG. 4A withoutthe requirement of additional compensating systems. However, suchcompensating systems can be used in connection with pump system 10 ofthe present disclosure to even further reduce pulsatility.

Piston extension members or cam lifters 120 can, for example, be placedin operative connection with cam shaft lobes 112 via cam followerassemblies 130. In the illustrated embodiment, cam follower assemblies130 include a bearing member or cam bearing 132 which is attached to camlifter 120 via extending members or bearing axle members 133 which passthrough passages 125 in cam lifters 120. In the illustrated embodiment(see FIGS. 3C-3E), cam follower assembly 130 includes a biasing elementsuch as a spring 134 which is retained within an interior cavity ofgenerally cylindrical cam lifters 120. In the illustrated embodiment,spring 134 is retained between a first abutment element (including, forexample, a pin 136, which passes through passages 126 in cam lifters120) and a second abutment member 137 (including, for example, a pin orconnector 137 (see, for example, FIGS. 3A and 3B) which passes through apassage 121 in lifter block 122 and through extending slots 128 formedin each of piston extensions 120). Spring 134 ensures that bearingmember 132 remains in contact with the corresponding cam lobe 112 andthus that piston 70 is drawn rearward within chamber 20 as the radius ofthat portion of cam lobe 112 in contact with bearing member 132 reduces(upon rotation of cam shaft 110; see, for example, FIG. 3A). Further,fluid pressure from inlets 54 a or 54 b will not cause flow of fluidthrough pump system 10. Fluid will flow through pump system 10 only uponrotation of cam shaft 110 via powered drive 100.

In the assembly of cam lifters 120 and cam follower assemblies 130,spring 134 is inserted into the body of cam lifter 120. Spring 134 ispartially compressed and held in place by insertion of spring retainingpin 136. The bearing and axle are then attached. Lifters 120 areinserted into the body or lifter block 122 of pump 10. When all camlifters 120 are inserted within lifter block 122, a retaining andanti-rotation device such as pin 137 is installed. Pin 137 is insertedinto slot 128 on the side of cam lifters 120 so that there is freemovement up and down in slot 128 but pin 137 prevents rotation of camlifters 120 within block 122, facilitating the tracking or following ofcam lobes 112 by cam follower bearings 132. Spring 134 is capturedbetween retaining pin 136 and anti-rotation pin or connector 137. Asrotation of cam lobe 112 moves cam lifter 120 upward (in the orientationof the figures), spring 134 is compressed. When the profile/radius r_(c)(see FIG. 4C) of cam lobe 112 drops or decreases, spring 134 appliesforce to cam lifter 120 to move cam lifter 120 downward (in theorientation of the figures) so that cam follower bearing 132 remains incontact with and follows the profile of associated cam lobe 112. If camfollower bearing 132 did not maintain contact with cam lobe 112, piston70 would not be pulled or retracted to its lowest (in the orientation ofthe figures) position and an incomplete fill of chamber 120 would occur,resulting in a decrease in pump output.

Pressurizing unit 15 can, for example, be placed in operative connectionwith lifter block 122 via a flange 18 which can be seated in a seating124 (see FIG. 2B). In this manner, the fluid contacting portions ofsystem 10, including pressurizing unit 15 can be readily removed fromconnection with drive mechanism 100. Pressurizing unit 15 can bedisposable (for example, on a per-patient, per time or other basis) to,for example, reduce or eliminate the risk of cross-patientcontamination. Pressurizing unit 15 can, for example, be formedrelatively inexpensively from polymeric, metallic, ceramic and/or othermaterials by any number of processes including, molding, injectionmolding, coinjection molding, extrusion, machining, etc.

In the illustrated embodiments, inlets 54 a and 54 b are in fluidconnection with a manifold or fluid distribution system 150, whichincludes a conduit or channel 152 therein (see FIG. 5B). Channel 152 isin fluid connection with ports 50 a through 50 e, which are in fluidconnection with inlet channel 50. A sealing member 154 is slidablypositioned within channel 152. The position of sealing member 154 can,for example, be controlled by control member 156. Control member 156can, for example, be an extending member to which force is applied(manually or in an automatic or semiautomatic manner) to slide sealingmember 154 within channel 152 (see, for example, FIGS. 5A and 5B).

As illustrated, for example, in FIG. 5B, the position of sealing member154 in conduit can be used to control the amount of (or ratio of) fluidA and fluid B entering pressurizing unit 15. In FIG. 5B, sealing member154 is positioned so that three ports (ports 50 a, 50 b and 50 c) are influid connection with fluid source A, while two ports (ports 50 d and 50e) are in fluid connection with fluid source B. If fluid source A andfluid source B are at approximately the same pressure and ofapproximately the same viscosity, the fluid entering pressurizing unit15 (and exiting pressurizing unit 15) will include approximately 60% byvolume fluid A and approximately 40% fluid B. In the embodiment of FIG.5A and FIG. 5B, the relative amounts of fluids A and B can be varied inapproximately 20% increments by the positioning of sealing member 154between ports 50 a through 50 c. The varying of the fluid ratios can,for example, be adjusted via a number of variables including, forexample, the number and dimensions of the one or more fluid ports influid connection with channel 152.

In the systems describe above, a plurality of pistons are controlled bycams that are fixed to a common shaft. Testing of cam-driven pumps hasshown that pulsatility or the degree of pulsatility changes as afunction of flow rate and pressure. In the cam-driven systems describedabove, cams and systems associated therewith are designed to reduce thiseffect.

Alternatively, one of, a plurality of or all of the drives or pistonscan be controlled independently in, for example, its timing, velocity,and position. In such an individually controlled piston pump, the pistonacceleration and velocities can, for example, be optimized for theconditions experienced at a certain time. For example, the start-up of apiston can be advanced in time relative to the previously actuatedpiston, thereby beginning pressurization resulting from the pistonsooner to reduce or prevent a pressure drop between pistons (as, forexample, illustrated in the pressure waveforms described above incertain cam-driven systems).

In a number of embodiments, an independently controlled drive isprovided for each piston of a pump system. Such a pump can, for example,have as few as two pistons. However a two-piston pump system has adisadvantage in that the fill time must be shorter than thepressurization portion of the piston cycle. In light of thisdisadvantage, three or more pistons/cylinders provide an advantage.

Each of the pistons can, for example, have a computer controlled drivein operative connection therewith. Such drives can, for example, belinear motors. A linear motor is an electric motor in which the statoris unrolled so that, rather than producing torque associated withrotation, the motor produces a linear force along its length.Alternatively, a traditional or standard motor can be used in connectionwith a linear drive (that is, a rotary-to-linear drive system).

Determination of individual piston control for a pump system can, forexample, be based on running parameters such as total flow output andpressure. For example, a lookup table or chart or an algorithm can bestored in memory for access by a processor to, for example, set timingand individual piston velocities to achieve a desired goal ofnon-pulsatile flow.

Furthermore, additional feedback data or information can be provided tothe processor from one or more sensors (for example, output pressure asmeasured by a pressure transducer) to effect control in the manner of aservomechanism. The system can, for example, anticipate required needsand use servo feedback to fine tune or adjust the system variables orparameters to achieve a desired result of flow with little or nopulsatility. Control inputs can, for example, include piston position,piston velocity, force on a piston, total flow output (as, for example,measured by a flow meter), output pressure (as, for example, measured bya pressure transducer), and individual chamber pressure (as, forexample, measured by pressure transducers).

FIG. 6A illustrate a pump system 210 including independent control ofeach of a plurality of pistons 222 (three, in the illustratedembodiment) reciprocally movable or slidable within three pistonchambers 220. Piston chambers 220 are in fluid connection with a commonoutlet channel 230. In the illustrated embodiment, each of pistons 222is in operative connection with an independently controllable lineardrive motor or linear motor 240 via a lifter or piston extension member250. Each linear motor 240 independently controls a piston 222operatively connected thereto. Linear motors 240 can, for example, becontrolled by a control system 260 that, for example, regulates thevelocity and positions of pistons 222. Control system 260 can, forexample, include one or more computer processors. The output and thefilling of each piston 222/cylinder 220 pair can, for example, becontrolled throughout each cycle. One or more sensors 280 (for example,one or more pressure sensors and/or flow sensors) can, for example, beplaced in connection with pump system 210 (for example, in connectionwith outlet channel 230 or in connection with the each of chambers 220)to provide feedback to control system 260 to effect independent controlof each of pistons 222.

Similar to the pump systems described above, pump system 210 can includea pressurizing unit 215 that can, for example, be placed in operativeconnection with lifter block 234 via a flange 218 which can be seated ina seating 236. In this manner, the fluid contacting portions of system210, including pressurizing unit 215, can be readily removed fromconnection with the drive mechanism as described above.

FIG. 6B illustrates a pump system 310 including independent control ofeach of a plurality of pistons 322 (three, in the illustratedembodiment) reciprocally movable or slidable within three pistonchambers 320. Similar to pump system 210, piston chambers 320 are influid connection with a common outlet channel 330. In the illustratedembodiment, each of pistons 322 is in operative connection with anindependently controllable rotary motor 340, which drives a linear drive342 such as a ball screw or rack and pinion via a lifter or pistonextension member 350. In the illustrated embodiment, each linear drive342 is a ball screw including a coupler 344 to connect a ball screw 346to each motor 340 (for example, a servo motor). Each ball screw 346cooperates with a ball nut 348 connected to a rearward end of a pistonextension member 350.

Each motor 340 independently controls a piston 322 operatively connectedthereto. As described above, motors 340 can, for example, be controlledby a control system 360 that, for example, regulates the velocity andposition of each of pistons 322. Control system 360 can, for example,include one or more computer processors. The output and the filling ofeach piston 322/cylinder 320 pair can, for example, be controlledthroughout each cycle. Rotary encoders 370 can, for example, beoperatively connected to motors 340 to assist in effecting controlthereof. One or more sensors 380 (for example, one or more pressuresensors and/or flow sensors) can, for example, be placed in connectionwith pump system 310 (for example, in connection with outlet channel 330or in connection with the each of chambers 320) to provide feedback tocontrol system 360 to effect independent control of each of pistons 322.

Similar to the pump system 210, pump system 310 can include apressurizing unit 315 that can, for example, be placed in operativeconnection with lifter block 334 via a flange 318 which can be seated ina seating 336. In this manner, the fluid contacting portions of system310, including pressurizing unit 315, can be readily removed fromconnection with the drive mechanism as described above.

The foregoing description and accompanying drawings set forthembodiments at the present time. Various modifications, additions andalternative designs will, of course, become apparent to those skilled inthe art in light of the foregoing teachings without departing from thescope hereof, which is indicated by the following claims rather than bythe foregoing description. All changes and variations that fall withinthe meaning and range of equivalency of the claims are to be embracedwithin their scope.

What is claimed is:
 1. A fluid mixing system comprising; an extendingchannel; at least two fluid inlet ports in fluid connection with theextending channel, wherein the at least two fluid inlets ports arepositioned at different positions along the extending channel and the atleast two fluid inlet ports are configured to introduce at least twofluids into the extending channel; at least one outlet port in fluidconnection with the extending channel and positioned between the atleast two fluid inlet ports; and a sealing member in sealing engagementwith the extending channel, wherein the sealing member is movable withinthe extending channel to adjust a volumetric ratio of the at least twofluids.
 2. The fluid mixing system of claim 1, further comprising aplurality of spaced outlet ports in fluid connection with the extendingchannel.
 3. The fluid mixing system of claim 2, wherein the spacedoutlet ports are positioned within the channel between the positions ofthe fluid inlets.
 4. The fluid mixing system of claim 3, wherein theposition of the sealing member relative to the plurality of spacedoutlet ports adjusts the volumetric ratio of the at least two fluids. 5.The fluid mixing system of claim 4, wherein the volumetric ratio of theat least two fluids are further adjusted by changing variables selectedfrom the group consisting of the number of fluid outlet ports, thedimensions of the fluid outlet ports, and combinations thereof.
 6. Thefluid mixing system of claim 1, wherein the volumetric ratio of the atleast two fluids is further adjusted by changing variables selected fromthe group consisting of the number of fluid outlet ports, the dimensionsof the fluid outlet ports, and combinations thereof.
 7. The fluid mixingsystem of claim 1, wherein the fluid mixing system is in fluidconnection with inlets of a plurality of chambers of a pump system. 8.The fluid mixing system of claim 1, wherein the fluid mixing system isin fluid connection with the inlets of a plurality of chambers of thepump system through the at least one outlet port.
 9. The fluid mixingsystem of claim 8, wherein each of the plurality of chambers of the pumpsystem comprises a piston slidably disposed therein.
 10. The fluidmixing system of claim 9, wherein each of the plurality of chamberscomprises at least one of the inlets through which fluid is drawn intothe chamber and an outlet from which fluid is expelled from the chamber.11. The fluid mixing system of claim 10, wherein fluid is drawn into thechamber and expelled from the chamber by reciprocal movement of therespective piston disposed therein.
 12. The fluid mixing system of claim11, wherein the outlet of each of the plurality of chambers is in fluidconnection with a common outlet channel.
 13. A fluid mixing systemcomprising; an extending channel; at least two fluid inlet ports influid connection with the extending channel, wherein the at least twofluid inlets ports are positioned at different positions along theextending channel and the at least two fluid inlet ports are configuredto introduce at least two fluids into the extending channel; a pluralityof spaced outlet ports in fluid connection with the extending channeland positioned between the at least two fluid inlet ports; and a sealingmember in sealing engagement with the extending channel, wherein thesealing member is movable within the extending channel such that theposition of the sealing member in the extending channel relative to theplurality of spaced outlet ports adjusts a volumetric ratio of the atleast two fluids, and wherein the plurality of spaced outlet ports arein fluid connection with inlets of a plurality of chambers of a pumpsystem.
 14. The fluid mixing system of claim 13, wherein the systemcomprises five outlet ports and five chambers, each chamber having aninlet in fluid connection with a respective outlet port on the fluiddelivery system and each chamber comprising a piston slidably disposedtherein
 15. The fluid mixing system of claim 13, wherein the volumetricratio of the at least two fluids is further adjusted by changingvariables selected from the group consisting of the number of fluidoutlet ports, the dimensions of the fluid outlet ports, and combinationsthereof.